can i run mac os catalina on a mid 2009 macbookPro that is currently running OS X el capitan so that i can use sidecar

Even if you could run Catalina (which as Niel says, you can't) your Hardware does not support sidecar.

No.

(179757)

Depending on exactly model, it may have a Mini DisplayPort, which can be adapted to HDMI to connect to your TV set.