I designed a number and blurred the outline. When I print it, it comes out a blacked out square block around the number. No blur effect. Does the blurring need to be changed to a different format ?

No. There's a bug with the current Windows 64bit version of Inkscape that makes printing of partially transparent parts of the drawing turn all black.

As a workaround, create a (large) white rectangle and put that below your drawing.
Or export to png, then print from a different program.
Yon can also switch to the 32bit Windows version, which doesn't suffer from that problem.