Hi there

Do you mean:

1. How many worksheet can you have in a workbook? (A) There is no
fixed limit by number, but you are limited by the memory on your
machine.

2. How many worksheets are in a specific workbook? (A) You could use
a macro to count this, a user defined function perhaps. Something
like:

Function SheetsCount()
SheetsCount = ThisWorkbook.Sheets.Count
End Function

You could apply this in a range in a sheet as follows:
=SheetsCount()