How old was Joseph when Jacob came into the land of Egypt?
Joseph was 37 years old when the dearth broke out across the land . When Joseph’s brethren came to Egypt on their second trip, Joseph revealed who he was, and he instructed his brethren to fetch their father to come and sojourn in Egypt during the famine.
During this instruction, Joseph provides information on how long there is left of the dearth in Genesis 45:6 :
For these two years [hath] the famine [been] in the land: and yet [there are] five years , in the which [there shall] neither [be] earing nor harvest.
Genesis 45:6
At the time of Joseph’s instruction to his brethren, he would have been 39 years old (37 years old at the start of the famine, plus 2 years later).