what app for Mac is comparable to microsoft Excel?

You can either subscribe to Microsoft 365 or you can make a one-time purchase. See: https://products.office.com/en-us/buy/compare-microsoft-office-products-for-mac?ms.officeurl=mac-compare-redir

Or use the free Microsoft Office on the web: https://products.office.com/en-us/free-office-online-for-the-web

Or Google Docs: https://www.google.com/docs/about/

Other options include using the free and very good Libre Office https://www.libreoffice.org/

or Apple's Pages and Numbers

Apple have their own suite of software and an excel replacement is titled Numbers. I use this app everyday on my iPad and it’s great. Does everything I need.

The Numbers app and of course you can get a web based app or you can buy Office for Mac 2019 or subscribe to Office 365. In short you have many alternatives.