The return date is 3 0 4
Explanation
In the letter, it is mentioned that the school will reopen after 29th of April. Thus, the tentative date of the school to reopen is 30th of April. The three digit return date is 3 0 4
3 0 4 because 30 is the date when the school will reopen and 4 is the month i.e., april when the school will reopen.