The process of legally converting a business to an employee-owned cooperative can vary significantly depending on what jurisdiction you're in. There's different criteria for creating one (some places might require more than 3 directors to create a Coop) and all sorts of statutory considerations unique to wherever you are.
If you're serious about doing this, I would sincerely recommend reaching out for legal advice first. This is your livelihood, and you do not want to make a mistake that creates difficulty down the line. Depending on where you live, there may be a public interest organization, or business law clinic, that can provide some legal information for free. You could look up "(where you live) non profit legal assistance" and see if anything shows up.