Looking for If/Then function

Question

I have a workbook comprised of forty-something Tabs of zip codes that each contain lists of Store Numbers. I need to state NEXT TO each store number either "Legacy" or "Swipe Up". There are thousands so it's too long to do manually with a drop-down selection. The source list of which the stores are "legacy" vs "swipe up" is under the first tab named "legacy vs swipe up" in my workbook.

How would I make this a function?
I have added a screenshot of my workbook

I was thinking an If then function would work but I am not sure of the formula layout.

This is the layout of my "Legacy vs Swipe up" tab looks like

Answer 1

A formula using the XLOOKUP function will give you the result that you are looking for.

The function is structured like this.

=XLOOKUP(lookup_value, lookup_array, return_array, [if_not_found]) 

Your formula would look like this.

=XLOOKUP(B3,'legacy vs swipe up'!$B$2:$B$15,'legacy vs swipe up'!$A$2:$A$15,"MISSING store number")

For your purposes, extend the lookup_array and return_array in the formula to include the used cell in the legacy vs swipe up worksheet. Example: If your last cell was 6000, then $15 would become $6000.

Added some random data to the legacy vs swipe up worksheet so that there were store values to match the store values being looked up.