As a general rule, multimeters, at least the inexpensive variety, were not originally designed for measuring the frequency of a signal. That's somewhat old school. These days you may well be able to get a Multimeter capable of measuring signal frequency but I do not know much about these, how well they work, how much they cost. If you found one on E-bay, the Seller of such a technical product should provide some Specs on this so you can read and find out what it can do before purchase.
I'm from the older school, and have not re-visited electronics school in a long time.... which is to say, outside of having an O'scope, I'm not sure what less expensive options there may be out there today for a cheap frequency measuring tool or "meter".
FWIW, here is a reference to a fairly simple to build multi-freq Zapper. Maybe save this for future experimenting. Of note, this circuit tutorial also mentions that a Digital Multimeter capable of measuring Frequency can be bought commercially for $50