How can I add more than one plan tier with Stripe?

//api/stripe
import { auth, currentUser } from "@clerk/nextjs/server";
import { NextResponse } from "next/server";
import { prismadb } from "@/lib/prismadb";
import { stripe } from "@/lib/stripe";
import { absoluteUrl } from "@/lib/utils";


const billingUrl = absoluteUrl("/billing");

export async function GET() {
  try {
    const { userId } = auth();
    const user = await currentUser();

    if (!userId || !user) {
      return new NextResponse("Unauthorized", { status: 401 });
    }

    const userSubscription = await prismadb.userSubscription.findUnique({
      where: {
        userId,
      },
    });

    if (userSubscription && userSubscription.stripeCustomerId) {
      const stripeSession = await stripe.billingPortal.sessions.create({
        customer: userSubscription.stripeCustomerId,
        return_url: billingUrl,
      });

      return new NextResponse(JSON.stringify({ url: stripeSession.url }));
    }

    const stripeSession = await stripe.checkout.sessions.create({
      success_url: billingUrl,
      cancel_url: billingUrl,
      payment_method_types: ["card", "Paypal"],
      mode: "subscription",
      billing_address_collection: "auto",
      customer_email: user.emailAddresses[0].emailAddress,
      line_items: [
        {
          price_data: {
            currency: "USD",
            product_data: {
              name: "Plume Pro",
              description: "Gain Full Access",
            },
            unit_amount: 7999,
            recurring: {
              interval: "month",
            },
          },
          quantity: 1,
        },
        {
          price_data: {
            currency: "USD",
             product_data: {
              name: "Plume Plus",
              description: "Gain Full Access",
            },
            unit_amount: 3999,
            recurring: {
              interval: "month",
            },
          },
          quantity: 1,
        },
      ],
      metadata: {
        userId,
      },
    });

    return new NextResponse(JSON.stringify({ url: stripeSession.url }));
  } catch (error) {
    console.log("[STRIPE_GET]", error);
    return new NextResponse("Internal Error", { status: 500 });
  } 
}

"use client";

import { usePlanModal } from "@/hooks/use-plan-modal";
import {
  Dialog,
  DialogContent,
  DialogDescription,
  DialogHeader,
  DialogTitle,
} from "../ui/dialog";
import { Separator } from "../ui/separator";
import { Button } from "../ui/button";
import { useToast } from "../ui/use-toast";
import axios from "axios";
import { useState } from "react";

export const PlanModal = () => {
  const planModal = usePlanModal();
  const { toast } = useToast();
  const [loading, setLoading] = useState(false);

  const onSubscribe = async () => {
    try {
      setLoading(true);
      const response = await axios.get("/api/stripe");

      window.location.href = response.data.url;
    } catch (error) {
      toast({
        variant: "destructive",
        description: "Oops! Something went wrong.",
      });
    } finally {
      setLoading(false);
    }
  };
  return (
    <Dialog open={planModal.isOpen} onOpenChange={planModal.onClose}>
      <DialogContent>
        <DialogHeader className="space-y-4">
          <DialogTitle className="text-center">Upgrade your Plan</DialogTitle>
          <DialogDescription className="text-center space-y-2">
            Choose a plan that meets your needs.
          </DialogDescription>
        </DialogHeader>
        <Separator />
        <div className="flex items-center justify-between">
          <p className="text-2xl font-plus font-medium">
            $39
            <span className="text-sm font-normal">.99</span>
          </p>
          <Button size="md" onClick={onSubscribe}>
            Subscribe
          </Button>
        </div>
      </DialogContent>
    </Dialog>
  );
};

I am building my app using Nextjs and Stripe, which have multiple plans for users to subscribe to. This is the first app I have built with various tiers and I am failing to find a way to make it work. So, the help I am seeking is to know if there is a way I can make my plans in a single API folder(if so, how), or if I will have to create different API files for each tier. The way I did it above just adds up the two tiers and the checkout is $119.98.