How to track inventory/materials that get used by our landscaping services side, to each job, instead of having everything in inventory on our material sales to customer?

I have quickbooks ONLINE. I have searched for several hours... I have a landscaping services business, and a material supply business. They are joined, under same name, so we run under same quickbooks. I can't do track inventory on anything because I can't separate what the services side takes. I can have them tell me/record it/track it, but how do I take it out of inventory and post it as a cost to a project? Everything is being entered as a sales of product right now (which DOES work for both in the end) but doesn't help me actually having ANY idea of what I actually have on hand, in the yard, to sell! Please help me figure out how I can bring in $10k worth of product into inventory properly, and move what the services side uses out of inventory, while connecting it to projects (for costing reports), and then being able to always know exactly what I have in stock!