Can anyone please help myself and my child locate her father, so that he can take a dna test and my daughter and grandkids can finally know their family on the other side?

Family Court in your area (or whichever branch handles these things in your State) when you file for support. They will require DNA testing before a support order is issued so they will locate him.

That is the easiest way.

You might try a website that offers whitepage information. Like a nationwide phone book. Its Get the 411 on Anyone with Free White Pages, People Search and Online Directory

If the child is over 18, then there is nothing you can do to force a DNA test unless the possible father is willing to take one.

Since you said daughter and grandchild I would expect the child is far past 18 now.