"Whole day" or "all day"?

From the choice you have given

I'm there all day

is correct.

A possible phrase using whole would be

I'm there [for] the whole day

Without the article the your second option doesn't make sense.

Another option is

I'm there for 24hrs


Definitely:

I'm there all day

The other expression is ungrammatical


Whole is almost always used with a preceding article (the/a/an), so something like I ate whole pie is invalid, whereas I ate the whole pie or I ate a whole pie are perfectly valid. The same situation applies to whole day.