During the quarantine period my adult son watched my younger children for a fee while I worked. What tax form do I need to prepare for him and how do I report that?

[Divaami]

The total about was less than $3000.

[MinhT1]

You can claim the child care expenses you paid to your adult son (if he is not your dependent).

As a private person paying child care, you do not need to provide him with any tax form. You just have to provide his name, address and SSN on your tax return.

Your son will have to report the amount received as self-employment income on his own tax return.

[Hal_Al]

If you are  claiming the dependent care credit, your son will need to report the income.  Otherwise, it's essentially optional.  You and he can treat it as a gift rather than calling it pay.