Target date funds are a “basket” of a funds designed for your age. You would want a 2040 fund. At your age, most experts would recommend about 50% in US stocks, 35% to 40% in world stocks and 10% to 15% in bonds.

A 2040 fund will be made up of about three to five mutual funds at those percentages. As you age, the percentages of each will adjust with you.

The Vanguard 2040 fund would be my recommendation for you. Because it’s already three to five funds, it’s all you need.