Web page domain

[bikes136]

Hello everybody!
We have a website that we´ve been using for about three years and has now a quite good ranking position on Google search.
Now we have created a new e-commerce website with worpress, beautiful but of course with still no positioning.
My question is: if I re-direct the old website into the new one, deleting the old page content, will I lose the positioning that that domain gained? Or will be a clever trick?
I hope my question make sense and that somebody could help me resolving this issue.
Many thanks in advance.