The easy way is to right click on the tab for File 1 and choose "Move or copy..." and tick the "Create a copy" box. I'd select "Move to end".

Double click on the tab for the new copy and rename it as File 3. You now have an exact copy of the sheet File 1 called File 3.

On the new sheet File 3, put this formula in cell D2: =VLOOKUP($A2,'File 2'!$A:$C,3,FALSE) ... then copy down to the last row. This looks for the SKU in column A on the sheet File 3 in the sheet File 2, column A and, if there's a match, returns column 3 ... the updated quantity.

If you did decide to copy File 2 and look up the price in File 3, the formula would be: =VLOOKUP($A2,'File 1'!$A:$D,3,FALSE). In fact, as you're not interested in the quantity, it could just be: =VLOOKUP($A2,'File 1'!$A:$C,3,FALSE) ... spot the difference?

Hope this helps.

Regards, TMS