Is it correct grammar to say several person?

"People" is the usual plural of "person." However, you can say "persons" to emphasize the individuals. So... 3,908,000 live in Guadalajara. But I spoke to only three persons that night: the cab driver, the wino, and the ballerina. In the second example you could also say "people."

Special circumstance: The police keep files on missing persons (not missing people).