Ive made many attempts and come close but not quite to what Im trying to do.

I have numbers in column A (sheet 1). I also have two columns, columns A
and B, of numbers in another spreadsheet (sheet 2). I need a formula that
says if A2 in sheet 1 matches a number in column B in sheet 2 insert the
numbers on that row from column C.

On the example below, for row 1 on sheet 1, Excel should insert 631085552 in
a new cell on row 1 because column A matches column B (row 2) on sheet 2. I
hope I explained this well enough.
Sheet 1 Sheet 2
Column A Acct_BAN Column A Acct BAN
Column B Acct #
108459216 640239555
108249314
119659211 631085552
108459216
129859214 637755184
116229317
141559217 602374342
177756211