We use the plural form "times". What is the difference between "how many times did I tell you?..." and "how many times have I told you?. There is no real difference, the first sentence is clearly stating or suggesting it was in the past, like when someone has told you several times in the last (past) few days. The second sentence could be referring to either in the past before now (today) and/or also now (today/this morning/this afternoon/this evening). The second sentence is the most common and natural way to phrase it, and it is used frequently whether or not the speaker is referring to now, or over the previous days/weeks etc. So colloquially there is no difference to many speakers, it is only in the classroom when analysing the grammar that there are very subtle differences.

John's answer is good. In general, if you were looking for a numerical answer, you'd use "did". How many times did you tell her that the report was due on Friday? (Was it once? Was it twice?) How many times have I told you not to put your elbows on the table during dinner? (This is a rhetorical way of saying 'I've told you lots and lots of times not to put your elbows on the table. Why are you still doing it?')

Sorry, it is "time", not "tome".

Hey Ethan! I believe the phrase you're talking about is "how many times did I tell you?" The phrase "how many tome have I told you, includes the word "tome" which isn't the right word for this phrase. Tome means "a book, especially a very heavy, large, or learned book.".

The right answer is “how long” have I told you. The sentence “how many time have I told you” is incorrect.