I have numbers that represent code/state and would like to combine them in
one cell (Column B) where the "xxxx".

Example:

A B C
Atlanta
00100
3000 xxxx 4930
3001 xxxx 5690


Results - I looking for

1 A B C
2 Atlanta
3 00100
4 3000 300000100 4930
5 3001 300100100 5690


Column A4:A5 = code
Column $C$3 = state
Column B = formula to combine the two (code_state)