Donald Trump knew exactly what the charges were. They were specified in the indictment.
New York Penal Law § 175.10: Falsifying business records in the first degree
A person is guilty of falsifying business records in the first degree when he commits the crime of falsifying business records in the second degree, and when his intent to defraud includes an intent to commit another crime or to aid or conceal the commission thereof.
The statue does not require that the defendant actually commit the underlying crime, only that there was intent. Thus there is no requirement of a prior conviction of the underlying crime(s). In the juries deliberations, they will determine it the defendant committed the underlying crime(s) however, the defendant does not have to be charged with the underlying crimes. Such charges both state and federal could be forthcoming.
The underlying crimes, violation of federal and state election laws are in the prosecution's opening and closing statements and most likely in discovery documents.