How do I fill a hole in basement floor?

You can purchase bagged ready mix to fill it in, You should make sure the dirt is packed well. You will have a seam where it meets the existing concrete but there's nothing you can do about that.

The ready mix you should purchase is a Just Add Water type. It can be mixed in a wheel barrow with a hoe. The pour into the hole. Using a trowel, spread evenly and smooth the top. Dampening the trowel as the concrete hardens will help to make it smoother. If you've ever frosted a cake, it's similar to trying to get a smooth finish on that.

Neva,

You do not want the soil to absorb all the moisture from the concrete as it cures. Tamp the soil firmly, put down a layer of 6 mil plastic, and then add a few inches of gravel. This will provide the best base to help prevent cracking in the future. Use as little water as possible in your mix. Let your mix settle and begin to cure before troweling the finish.

All you need is a bag of concrete mix. No need for plastic or gravel. None was there in the first place. Dampen the sides of the old concrete so it doesn't wick moisture out of the new concrete. Mix the concrete, pour it in, level with a trowel.

Was the hole for a sump pump? You might need it, check into that before filling it in.

i don’t k is what it was for but it has been plugged up for many many years now. We had a board over it and I just want to fill it in finally.