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.