Autofill formula that references two columns

I would really appreciate help on how to autofill this formula in my spreadsheet! I've been trying to look online for an answer but I can't find what I'm looking for

I THINK this can be accomplished by the INDEX formula but I don't know enough about it.

The first two "sets" of the formula are below. The formulas reference data from another sheet in my workbook (titled 'TO PRINT') that has data in columns A & B. Each formula "set" contains two lines, which both reference the same row, however each line references a different column (A or B). I want to be able to drag this down so the next formula "set" would reference A4 and B4, followed by A5 and B5, etc. Right now if I try to drag this down it skips rows, it does not autofill consecutively.

[TABLE="width: 2018"]

[tr]

[td]

=IF('TO PRINT'!A2="","",CONCATENATE("SwapUDP:" & 'TO PRINT'!A2))

[/td]

[/tr]

[tr]

[td]

=IF('TO PRINT'!B2="","",CONCATENATE("Get:C:\Users\test\Desktop\COMM TESTING\" & 'TO PRINT'!B2 & ".001"))

[/td]

[/tr]

[tr]

[td][/td]

[/tr]

[tr]

[td]

=IF('TO PRINT'!A3="","",CONCATENATE("SwapUDP:" & 'TO PRINT'!A3))

[/td]

[/tr]

[tr]

[td]

=IF('TO PRINT'!B3="","",CONCATENATE("Get:C:\Users\test\Desktop\COMM TESTING\" & 'TO PRINT'!B3 & ".001"))

[/td]

[/tr]

[/TABLE]

Re: Autofill formula that references two columns

Thank you so much Derk!! This does exactly what I need it to.