In Mark 5, about how many pigs drowned after Jesus let the unclean spirits enter them?

Answer: Two thousand

The unclean spirits entered the pigs, and the herd of about two thousand rushed down the steep bank into the sea and drowned.

“He gave them permission, and the unclean spirits came out and went into the pigs, and the herd of about two thousand rushed down the steep bank into the sea and drowned in the water.”— Mark 5:13 (BSB)