The average human woman has a surface area of 1.6 m2 (1.9 for men, but we're doing the lighter to give the ants the best chance).

We'll assume the person is laying down to give the maximum surface area, so about half of their surface area is accessable for the ants to lift from (in reality it'd be a little less since humans aren't perfectly cylindrical nor 2D). So 0.8m2.

An ant has an average surface area of 0.8949 cm2 or 0.00008949m2. Same deal with the human, we'll only be using half this number, so say an ant takes up 0.00004475m2 of space.

This means that there will fit about 18324 ants underneath a human laying down. (Note that the ants are in a single layer. No, stacking ants on top of each other won't make them able to lift more. Just like if two people can each lift 100lbs, they can lift 200lbs if they lift together, but not by going piggyback)

Ants weigh between 1-5 mg. Again, best case scenario, we'll assume 5mg or 0.005g. If an ant can carry 50x its body weight, then each ant can carry 0.25g.

18324 ants each able to hold 0.25g is a combined strength of 4581g or 4.581kg or about 10lbs. The average human woman weighs about 170lbs, which is nowhere near our total, even accounting for all our assumptions and rounding

So unfortunately, no, ants can't carry a person.

As for how many ants it would take, let's assume the same 170lbs (~77.11kg or 77110g), 0.005g ant weight, and 50x strength, but now let's say the woman has infinite surface area and as many ants as we want can fit under her.

We'll assume the person is laying down to give the maximum surface area, so about half of their surface area is accessible for the ants to lift from (in reality it'd be a little less since humans aren't perfectly cylindrical nor 2D). So 0.8m2.

All this assuming that ants don't have some weird 'stronger than the sum of their parts' thing that some animals have, of course.