Inserting values into a variable table

I am creating a function for inserting values into a table.

The problem is the tables have various names, depending on the userid.

i.e

email_inbox_a608ac4e-5215-4758-905e-78cfb809aebc

is for one user, while…

email_inbox_c86hce32-4758-905e-gfkk439d83jd

is for another.

I am trying in my sql, to pass the tablename as a parameter,

i.e

select * from $1 where messageid  = $2

but the compiler is not accepting it. What is recommended?

Thank you.