ITunes credit

iTunes may be terminated as an application, but Music, TV, and podcasts take center stage:

"iTunes forever changed the way people experienced music, movies, TV shows, and podcasts. It all changes again with three all-new, dedicated apps — Music, Apple TV, and Apple Podcasts — each designed from the ground up to be the best way to enjoy entertainment on your Mac. And rest assured; everything you had in your iTunes library is still accessible in each app. iCloud seamlessly syncs everything across your devices — or you can back up, restore, and sync by connecting the device directly to your Mac."

Answers to some of your iTunes questions: Old libraries, Windows, and more

See this post by turingtest2 in: ITunes Going Away - Apple Community

"The rumours of the death of iTunes have been somewhat exaggerated. iTunes is staying exactly the same except for those who install the next version of macOS 10.15 Catalina where the functions will be split between three new apps and Finder."

Your remaining credit will still be available for all of the purchases you need/want.

All of your iTunes purchases and credit will still be available through the Apps replacing iTunes

iTunes gift cards are valid 2 years from purchase

https://support.apple.com/en-us/HT202359