Compare 2 Columns & Copy Common Cell Rows

this is in reference to a question I asked some time ago in which I was given the following: =IF( COUNTIF(SHEET1!$A$1:$A$1200,SHEET2!A1),SHEET2!A1,"")

To summize as this is not quite working, I have two worksheets and in Column A are id#s. Worksheet 1 has100's more rows of data than Worksheet 2. I need to find the unique ids from column A in Worksheet 1 that match Unique IDs in worksheet 2.

I need to copy the row of cells from worksheet 1 where the unique id equals that u.id in worksheet 2. That row needs to be copied to Sheet 2 that has the same unique id, and after the pre-existing cells which are already present.

So for instance: if Sheet1 A100 = Sheet2 A24, then copy row A100from Sheet 1 and paste it to Row A24 of SHeet 2 start with the first empty cell- just say Sheet2 G24 as an example.

Using the formula I was given before, it finds matches, but the pasted rows are off. If the match occurs with Sheet 1 A450 and Sheet 2 A36, it will copy the value from ROW/SHeet 1 A36 instead of ROW/Sheet 1 A450