。
Don't forget to come here at 7 tomorrow.
Literal
Tomorrow here [to-に] 7-o'clock [at-に] come [nominalizer-の] [object-を] forget-not.
忘れるな is the plain negative imperative — literally 'don't forget.' The な after a plain dictionary form verb is a prohibitive marker, the negative counterpart to the plain imperative. Gruff, masculine, or parental. くる is plain-casual (kanji and hiragana mix is common in casual written Japanese).