Hi have a quaker model dvf50a-3-n and I know I at least need a thermostat for it. Luckily I have a manual for it. Any suggestions welcome

If it's a Heil Quaker furnace these folks sell parts. https://www.johnstonesupply.com/storefront/motors/blowers-draft-inducers/oem-replacement-draft-inducer-blowers/heil-quaker/c1027339-c1026815-c1028014-c1027479-p1.html