Download a free program called SPECCY which will show Make & Model of your Motherboard and other hardware installed. Also show all software installed.
This 2018 Dell Thread about your computer Inspiron 5675 mentions that your motherboard doesn't support 2nd Generation processors which means your Ryzen 3rd generation won't work either: Inspiron 5675, CPU compatibility - Dell Community
Dell Support for your PC has parts that are compatible with your motherboard including RAM MEMORY.
I highly suggest you open a DELL Support and find out exactly what hardware is compatible with your motherboard.
But you will need to replace the DELL Motherboard with a Motherboard that will support 3rd generation processors with the correct BIOS version and will also list what RAM MEMORY is compatible with the Matisse processor.
Note: I would also try to upgrade the PSU to a metal rated PSU of at least 750 -850 watts or higher.