INDIRECT within COUNTIF

Thank you in advance for any help you can lend.
- Column A of Sheet1 lists worksheets containing data: 'Data1' and 'Data2'
- Column B contains a COUNTIF function:
Cell B1: =COUNTIF(Data1!B:B,"Apple")
Cell B2: =COUNTIF(Data2!B:B,"Apple")

I want to alter the formulas in column B to use the INDIRECT function, while referencing the worksheet names that are in column A


Could someone please help with this?

Thanks, Sven