Storing a column count into an id

Can someone tell me how to fix this query? Basically I just want to do a select count on a column and then to store the result in a number or integer. It seems pretty simple, but I am really tired right now, so some help would be appreciated.

COUNTER INT;

SELECT COUNT ('CustomerId') INTO COUNTER FROM user_tables where table_name = 'Customers';

Here CustomerId is the column name. The query is not working as the result returned is zero.