[MBilal]

This will match both strings Like nume have JXFF1
so it will try match it with JXF you can see clearly both are different they are not matching.
if((strcmp(nume, "JXF", true) == 0))

about strfind it will find the JXF in the name of player.

wiki pedia.

(const string[],const sub[],bool:ignorecase=false,pos=0)

const string[] The string you want to search in (haystack).
here GetName(playerid) string You're searching in player name JXF

const sub[] The string you want to search for (needle).
JXF

strfind(GetName(playerid),"JXF",true)