The exact number of Israelites enslaved in Egypt after Jacob is not provided in the Bible, but we can make a rough estimate based on biblical accounts. When Jacob and his family first went to Egypt to escape the famine, they numbered 70 people (Genesis 46:27). Over the following generations, they grew into a large population.
The book of Exodus provides a clue regarding the population at the time of the Exodus, stating that about 600,000 men left Egypt (Exodus 12:37). If we include women and children, estimates range between 2 to 3 million people for the total population of Israelites leaving Egypt.
Therefore, while it’s impossible to give an exact number, it’s generally estimated that by the time of their enslavement and eventual Exodus, the Israelite population in Egypt was likely in the millions.