is the sentence correct

Hola L

Yes, as Marsha said, if the command is directed to a formal you (usted) the imperative form is the present subjunctive: coma - if the command is directed to an informal you (tú) then the imperative form is the verb conjugated in the third person singular of the present indicative (for most verbs): come 

But here are the Kwiziq lessons that explain all this:

Forming the imperative for usted/ustedes/nosotros/nosotras (affirmative and negative commands)

Forming the imperative of tú for most verbs (affirmative commands)

I hope this helps.

Saludos

Inma