Walaikumussalam
People those who going to Makkah from Jeddah their meeqat is Masjid e johfa.go there and do niyat for umrah there.
If one is unable to go to Masjid e Johfa then he/she can make nazr that I will wear my ehram from Jeddah then they can wear ehram at Jeddah and do the niyat there.
Wassalam
Syed Abul Qasim Rizvi