Member login – relation database help

I have a client who I created a site for and had a 3rd party company create them a member login mysql DB to where people can go register and upload a picture and edit their personal data. Well it went out of whack and I was wondering if I create them a wordpress theme that resembles their existing site can I use this DB info for wordpress? or is their a plugin for wordpress that allows members to create a profile page?

the site is https://undertheradaraz.com