If the person/company paying him had 'control' over his work, he was likely an employee.  If that is the case, go to line 1z of the 1040 and double-click it.  Double-click again.  Go to line i4 and enter the foreign wages.

If the person/company paying him did not have 'control' over his work, you need to determine if it is a business or 'other' income.  If the work was unrelated to his 'regular' work, it is likely 'other' income in which case you enter it on line 8 of Schedule 1.  If the work was very similar to his 'usual' work, it might need to go on Schedule C.

Yes, you need to convert it to US dollars.