How to create the own breadboard?

Breadboards are special, and you have to edit (and know how to edit) the underlying files to make them work correctly (and they are generally a lot of work!) If you post your part as a .fzpz file I’ll have a look at it (I have made a number of custom breadboards for folks over the years …)

edit:

Your likely problem is that that the drawing is dimensioned in px (the original breadboard svgs are.) in 72dpi Illustrator. Current Inkscape is 96dpi thus the difference in size. The result is you need to rescale the svgs and set the dimension to in (or mm) not px. This tutorial may help:

Peter