Can I get a confirmation receipt from IRS on accepting the amount I had paid in taxes while filing 2018 taxes?

The IRS does not issue any type of confirmation or receipt for taxes paid.

You cancelled check, bank or credit card statement showing the taxes paid is your proof of payment.

Provided enough time has elapsed since you sent your payment, your 2018 account transcript from the IRS will show whether or not your payment has been credited to your tax account:  https://www.irs.gov/individuals/get-transcript