commit or dispatch inside a callback [duplicate]

I have a function in my vue/nuxt project to authorize a payment method, and inside de callback I need to execute a commit and a dispatch but the syntax apparently is not correct.
Any help will be appreciated.

myFunction () {
      window.client.Payments.authorize({
        payment_method_category: 'payments'
      }, {
        purchase_country: 'ES',
        purchase_currency: 'EUR',
        locale: 'es-ES',
        billing_address: {
        },
        shipping_address: {
        },
      },
      function (res) {
        if (res.approved) {
**        this.$store.commit('checkout/setMyFunctionAuthorizationToken', res.authorization_token)
          this.$store.dispatch('checkout/finish')
**        }
      })
    },

I can’t use the ‘this.$store’ but I don’t how to do it.