Struggling to understand the Index/Match functions

I'm trying to reference two columns (A & B) in Worksheet A, match them with two columns (A & B) in Worksheet B; then return the Value of Worksheet B (Column C), into Worksheet A (Column C)

Hope that makes sense.
I've does some searching for using VLOOKUP function to do this, and most of my searching ends up in someone using an Index/Match function; so I'm guessing vlookup isn't the solution.
Here is the formula I tried using to accomplish this (in Column C, of Worksheet A). I'm sure it's a simple solution and I know I'm doing something wrong; but I can't figure it out.
=INDEX(WorksheetB!$A$2:$A$10,MATCH(1,IF(WorksheetB!A$2:A$10=A2,IF(WorksheetB!B$2:B$10=B2,1)),0))
I'm not sure if I'm heading in the right direction. I'm guessing because there's no reference to Column C in the function it doesn't know where to look. I'm not entirely sure. Looking for guidance.
Thank you!


Worksheet A

Column A	Column B	Column C
1	7	(worksheet B value)
2	7	(worksheet B value)
3	7	(worksheet B value)
1	11	(worksheet B value)
2	11	(worksheet B value)
3	11	(worksheet B value)
1	2	(worksheet B value)
2	2	(worksheet B value)
3	2	(worksheet B value)

Worksheet B

Column A	Column B	Column C
1	7	45
2	7	15
3	7	25
1	11	15
2	11	35
3	11	70
1	2	40
2	2	50
3	2	5

Thank you abousetta. That should help me in the future too.