Multiple IF''''s with Vlookup wrote...
This is the formula which I have:

=MID(L2,SEARCH(" vdi",L2)+1,4)

Now, I want to use multiple if statement in this formula.
....

I'm going to guess (sadly it's just a guess because you haven't yet
managed to be specific) you want to find the first of several possible
words in cell L2. I'll use the following sample array of words:
{"one","two","three","four"}. The first of these found in L2 would be
given by the formula

=INDEX({"one","two","three","four","none found"},MATCH(TRUE,
ISNUMBER(SEARCH(" "&{"one","two","three","four","*"}&" "," "&L2&"
")),0))

There's no need to use nested IF calls.