God told Abram his descendants would be enslaved and mistreated in a foreign land for how long?

Answer: 400 years

God said Abram's descendants would be strangers in a land not their own, enslaved and mistreated four hundred years.

“Then the LORD said to Abram, “Know for certain that your descendants will be strangers in a land that is not their own, and they will be enslaved and mistreated four hundred years.”— Genesis 15:13 (BSB)