dose GTX 1650 work with the Dell Optiplex 5000 SFF?

I think you know the answer ... 240w PS is like a little-baby PS.

But if it has the proper available GPU power-plug for it you can try it.

I ran a GTX-1660 in an old-Dell tower for a while (with upgraded PS) ... it's very close to the (legendary) GTX-1070 (in performance and power-requirements).

You really need a tower case ... to be able to have a proper-sized PS, some real (dual-slot) card-space, and some ventilation.

You can do it w 240 w psu but you need to be careful about power consumption in the pc.  Minimize other devices using power such as USB or HDD/ODD

Well, the 1650 draws 75 watts from the PCIe slot, so I would need to know your current CPU wattage and system draw at full load. You can get an inline tester and find out what the system draws at full load in a stress test. If it's a 65w chip and the system sips on power, it's completely possible, provided the card physically fits in the PC. If it does not, you still have the option of installing an Oculink to PCIe 16X adapter card in the PCIe slot, and you can get an Oculink dock to hook up to it that has its own PSU. If you take this approach and run the card outside the constraints of the case, you can use any GPU and pair it with the system.