Having Muhammad as a number plate
In the name of Allah, the most Beneficent, the most Merciful.
The Prophet of Allah Sallallahu Alahi Wasalam has said: ‘I have several names. I am Muhammad and I am Ahmad and I am Al Mahi (Eraser) by means of whom Allah erases kufr and I am Al Hashir (the gatherer) at whose feet the people will gather and I am Al Aqib (the successor). (Sahih Bukhari )
With regards to your question, as the name Muhammad is a common name and used by many the number plate you are keeping is not being attributed to the Prophet Muhammad Sallallahu Alahi Wasalam but rather to your father, hence, there is no form of disrespect being involved here.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham.