2.5mm Audio jack to micro USB
"2.5 mm jack" is a mechanical spec.  You also need the electrical spec.  What voltage does this jack provide?  At what maximum current?  Is it a regulated and de-glitched 5 V?  A direct connection to the car 12 V system?  Something else?

Measure what power comes out.  Only then can you decide what needs to be electrically between this jack and a USB charger output.  If the jack provides 5 V, then maybe you can just connect them directly.  If 12 V, then you have to assume all the nasty spikes on the car 12 V system come along with it.  You could then hack up the same charger you now plug into a cigarette lighter outlet to plug into this jack instead.