Someone has requested my four book box set however I do not know how many credits it is worth. I don't think it would be worth it to send it if its only worth one..I can't find out where to see how many credits I will get

If you have posted it with the ISBN on the box, then it's worth 1 credit.

If the books have their own ISBNs printed on them, you can just post them all separately and get 1 credit for each book. But there are no guarantees that one person will want or order all 4 books together.

If you really feel like they should be mailed as a set, then don't post them to your bookshelf .... instead you can also make a forum post and offer them in the Book Bazaar as a boxed set for 4 credits (provided that the books are not Wsh Listed) and see if you get any takers. If they are Wish Listed, then you can offer them as a set in the thread (in the Book Bazaar) for "Wishlist Multiples" and make a requirement that one person has to order the whole set.

And, the best place for questions of this type is over in "Questions About PaperbackSwap".

This forum is really normally specific to USPS and mailing issues. The other forum has more traffic and more people who will chip in with additional suggestions.

um, if someone requested it, doesn't aht mean you already posted it?  so the site has already determined the credit amount.