INDIRECT wrote...
I'm trying this:

I have a workbook named List with 25 worksheets named n1, n2,
n3,...,n25.

I have another workbook named Final with 25 worksheets named f1,
f2, f3,...,f25.

In workbook Final, worksheet f1, cell C2, I want to build a formula
to get the value of the cell B7 (workbook List, worksheet n1).
In workbook Final, worksheet f2, cell C2, I want to build a formula
to get the value of the cell B7 (workbook List, worksheet n2).
In workbook Final, worksheet f3, cell C2, I want to build a formula
to get the value of the cell B7 (workbook List, worksheet n3).
And so on...

Good. Not what you asked the time before this. You're learning about
details and precise specification. Good.

I'm going to assume that your worksheet names aren't really as simple
as n1, n2, f1, f2, etc. So best to create a table in the Final
workbook with worksheets names in Final workbook in the first column
and corresponding worksheet names in List workbook in the second
column. I'll assume this table is named Tbl.

Next, define the following names.

_CFN: =CELL("Filename",!$DX$32768)

_WSN: =MID(_CFN,FIND("]",_CFN)+1,32)

Then try the following formula.

[Final]f1!C2:
=INDIRECT("'[list]"&VLOOKUP(_WSN,Tbl,2,0)&"'!B7")

Copy this cell and paste into [Final]f2!C2, [Final]f3!C3, etc. The
single quotes in INDIRECT argument may not be strictly necessary, but
they'll save you lots of headaches in the long run.