Did you remove the old account? If so that usually removes the syncd data from the Google account which usually includes contacts. You need to have those contacts added to the Google account on your phone.
Assuming your old Google account still exists, go to Google Contacts (on a computer or laptop is easier), make sure you're logged into the old account (if not, log out [click on your picture or the generic silhouette) and log into the old account), then export (More/Export) a Google csv file of all your contacts to your computer.
Then log out, log into the new account, import (More/Import) the csv file you exported. The new account will have all the contacts the old account had.
If you've already deleted the old account, and you don't have a backup file, you're in for a lot of typing.