Can I use opamp to convert 5V DC into 10V DC?
Think about it.  Where does the opamp get 10 V from?  It comes from its supply voltage.  Opamps don't magically make more voltage.  They can only vary their output to voltages between the supply voltages they are given.

What a boost converter can do that a opamp can't, is to actually make a higher voltage than anything it is given.  If you only have 5 V, then a opamp can't give you 10 V, but a boost converter can.