H4 extension i 539

My husband h1b extension is under process . Our i94 expires in 2 months from now. I am about to file mine (h4) extension and for my minor kids too. Need to know howmany i 539 i need to fill?
How much is fees? Any suggestions ? Which documents to include apart frm one mentioned on uscis site? TIA

I have confusion on page 2, part 3.

2 (a) yes or no? My husband hi1 b ext petition is already under process with uscis, he is waiting for decision . I am now applying along with my kids.

Also 3(a) and 3 (b) what to select.

Also i am not able to type number in part 2 , 5(b).

I have ead but never worked , do i need to provide salary slip of my husband as mentioned in page 3,
Part 4 , 14th question ?

Do we need to put cover letter too in packet?

Since your husband’s H1B is not yet approved, you can select No and explain about it in Part 8 if you would like to.