Since visiting Kosovo visa-free is possible for Jordanian nationality, and Serbia is not as I search (not sure) so is it possible to cross the border from Kosovo to Serbia without Visa ? or I can take it from the border itself ?
As a national of Jordan, you do need a visa to enter Serbia. There is no provision for visa on arrival; you will need to obtain one in advance.
However, you can enter visa-free if you also hold a visa or residence permit from a Schengen country, the UK or the USA.
Remember one thing: if you entered Kosovo from anywhere other than Serbia, you can NOT cross from Kosovo to Serbia during the same visit. You need to go to Macedonia or Montenegro and enter Serbia from there