"I am ninety-one years old."
Translation:Dw i'n naw deg un oed.
I assume you mean the tag "you know" as opposed to the "Blah blah" bit. There are a couple of ways. I personally use "Ch'mod" which is a contraction of "Chi'n gwybod" and "T'mod" which is a contraction of "Ti'n gwybod". There is also "sti" which is a contraction of "(G)wyddost ti" which is a form of "Gwybod" though I don't know what the "Chi" variant of this is due to it not being one I come accross often.
So the old lady who wants to get some work done around the house for free might say "dw i'n naw deg un oed, t'mod/ti'n gwybod." That is good to know.