Use the formula `=A2&” “&B2`
If Last Name is in A2 and First Name is in B2, this returns `Last Name First Name`
Use the formula `=CONCAT(A2,” “,B2)`
Use the formula `=TEXTJOIN(” “,TRUE,A2,B2)`
Enter the formula in a new column and fill it down
Copy the results and paste as values if you want to replace formulas with text
Use Flash Fill by typing the combined name in the first row, then press `Ctrl+E`
Use the formula `=B2&”, “&A2` to get `First Name, Last Name` or `Last Name, First Name` depending on column order