Is it correct to use warmly welcome to our company?
It is not correct to say it exactly that way, but it would be
correct to say, "We warmly welcome you to our company." In this
case, "warmly" is an adverb modifying "welcome" used as a verb.
It would also be correct to say, "We would like to extend a warm
welcome to our company." In this case, "warm" is an adjective
modifying "welcome" used as a noun.