The minimum number of board members is set by state statute. Arizona requires one board member. Nonprofits do not need to be incorporated to receive tax exempt status from the IRS, but it is usually recommended.
You can convert an LLC to a nonprofit if the business entity is eligible under IRS Section 501(c)(3). 501(c)(3) nonprofits benefit from federal and state tax exemption and gain more access to funding resources.
In Arizona, you can convert an LLC into a nonprofit corporation by filing a Statement of Conversion. However, it's not as easy as just filing a form. You first need the approval of all LLC members, and you'll need to draft Articles of Incorporation and nonprofit bylaws as well.
You don't need to change anything. Form your 501c3 and get your approvals to operate from the IRS. Then move the assets of the LLC to the 501c3 in the form of a gift or donation. The LLC will then have no assets and can then be dissolved.