If I buy headphones (Cowen E7) and it says they are Bluetooth,will they work with my stereo even though it isn't Bluetooth? Isee no cableont?

YES says the manual. It has a place for a removable audio cable in case you need to or want to go wired. You may need an adapter and/or extension cable if your stereo has a 1/4" headphone jack.

You can buy a bluetooth transmitter for your stereo for only a few dollars.

Nope,

The bluetooth headphones will only function with a bluetooth transmitter such as a bluetooth capable stereo, smart phone, tablet, etc.

You have to be able to send a signal to your headphones from your stereo. You might be able to get a bluetooth adapter that will accept signals from your stereo then send them to your headphones. The cost of going wireless.

Only if it has a way to attach a cable. It comes with a 3.5 mm audio cable so I assume you can.