1) Enter 1 in an empty cell somewhere and copy it.
Select the range or the cells you want increased.
Right Click - Paste Special -Check "add" - OK

2) In C1 enter =A1&B1 then drag down as needed or double click the cross-hair at the right lower corner of the selected cell

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Using O365 v2503 - Did you know you can thank someone who helped you? Click on the tiny scale in the right upper hand corner of your helper's post