upgrade 1. to 3.0

hei,gays
my website use nop 1.90    i find  there is no good theme for 1.90,     so   i  want upgrade to 3.0    but  i  find  3.0 url  is  not   the  same as  1.90
so    who    can   help   me  how  to   solution  this   issule.
or     who  can   introduct   some  good   theme  for    1.90?
thank you  very  much!

clarify " i  find  3.0 url  is  not   the  same as  1.90"

i mean  my artical url  is like this    http://www.1234diy.com/news/15-news.aspx
if  i  upgread to  3.0  the url   will  change
is not usfull   seo