Sounds like those fleeces are pretty ancient and have been stored in plastic bags. Not good, but alpaca does store that way better then sheep fleece. Do you know how many alpaca the previous owner had? That would give you an idea of how old some of the fleeces are. You might be able to work out which are the newest ones, with the most likelihood of being usable, by how much dust and settled mank there is on the bags.
First off, you need to tip each bag out and take a peep. Spread the fibre out on a plastic sheet, check whether it's mouldy, has mice or a bee's nest in there, and whether it's full of veg stuff like hay, thistles, and so on. Smell it - if it smells fusty then I doubt a spinner will be interested, but you never know.
Each alpaca fleece will be different, not just for colour but also for quality. Many alpaca coats are very hairy (which is hell to remove by hand), but first shear ones tend to be nicer. The mill processors could process them for you if they are in good condition, into yarn or woven products to sell, but they are expensive as they need specialist equipment for alpaca.
If they're only suitable for disposal, I have no idea, sorry. Alpaca fibre doesn't have the tiny hooked scales along its length that sheep wool has, which is what makes it cling together for spinning easily, so it wouldn't be useful for my favourite use of lining potholes under stones (wool felts together and holds the stones in place)
For insulation you would need to treat it against vermin, but otherwise it's a wonderfully environmentally correct usage.
I get the impression that alpaca fibre is not nearly as valuable as keepers expect. Buy an expensive alpaca and surely you will be rich? Not at all - it's the breeder who will be rich and not the buyer. However, there are folk who have specialised in making a saleable products from their alpaca fibre, but they have developed it into a business, so just to use up what you've found will not be the same.