Show MySQL tables starting with prefix?

To list all tables with some prefix, "any number of symbols" wildcard (%), should be used.

_ is also a wildcard, representing any single symbol, and therefore it should be escaped.

Therefore, given your prefix is someprefix_, then

SHOW TABLES LIKE 'someprefix\_%'

would work

SHOW [FULL] TABLES [{FROM | IN} db_name]
[LIKE 'pattern' | WHERE expr]