Seems I purchased the wrong mesh extenders for my router - an Archer AX10 

I ordered, and received, 3 Deco X55 units

I wanted to extend my Archer router with a unified wifi ssid to the downstairs, and to outdoor security cameras, saw "mesh" and bought the wrong mesh.  More I look into things, the more I manage to become more confused. Like backhaul?

-- Do I pitch the Archer AX10 router, and plug the Deco into the ISP's modem (cable)? Then ethernet downstairs to another Deco, then wireless to garage for third? (or something like that?)

-- Keep router?  Plug one deco into the router, one deco into that rounter, then a third deco wireless, but disable router wireless, just use the decos for wifi, and router for rj45? 

Advantages/disadvantages to either solution?  Other than the disadvantage of throwing away a seemingly rock-solid and not that old router? 

Thanks in advance to all who read my woes.