Please help me! Maybe someone understands where it can be sold. Or teach you how to use it?
Has he been mining before passing away? Do you know if he had friends, family members, children etc he associated with that know alot about the mining or who are also involved in mining business? If you have such who understand mining really well and can be able to manage it then you may let them help you. Unfortunately, Sole Proprietorship or private business like that could be a bit hard to manage if the owner has passed away, so it's usually advisable to sell it off. But if you can find any who can properly manage it then do.
If your final wish is to sell the business, you should first of all try to see if there are willing buyers within you country/community. You could use Google to find miners around you, get their contact and ask them if they are interested in buying your late husband miner(or mining business) or perhaps they can teach you how to run the business profitably.
If you can't find any then I will suggest you go to this forum section called Mining and possibly ask your question or move this your post there. Here is the section link(I guess for Bitcoin mining):
https://bitcointalk.org/index.php?board=14.0Go there and ask your questions, it's a Mining-related section Hopefully you will find the right people/person to guide you on what to do with the mining farm.
Hope you have the receipt that proves the miners were purchased by your husband, just in case you need to sell them/it. And I wonder if you know what he has mined so far and possibly have authorized access to it. That will probably enable you determine whether it's profitable enough to continue mining, use it to take care of your family or continue from where he stopped.
Try to provide other proofs about the miners, like pictures(or probably video) as someone already suggested. This can help make things easy for for your helpers in this forum mining section.