You are talking about upscaling (up rezzing) your footage so you will take a small quality hit.
I would do it in After Effects for better quality, scaling and control than PPRo will offer.
Simply create a 2K Comp. Drop your footage into it and Scale it up till it fits.
Out put it as per your or lab requirements.
how to do it without loss of quality is there any tips
Shoot in 2K or better. If you upscale, you are trying to make up images from information that is non-existent and that will always entail quality loss.
Why do you need 2K? i what are you actually doing?
i am a filmmaker doing film now,but i have low budget that's why i choose canon 5d mark 3 it gives 1920x1080 but the film size is 2k what can i do for the best result
I am not sure why you say the film size (Neg) is 2K?
Are you doing a Film Out put from digital?
Best result...shoot 2k or better.
Otherwise ..Up scale as I suggested and use the tools in After Effects to optimise the image.
In reality..it will be fine. The up scale is relatively slight as per digram (but any upscaling is not best approach or workflow)
Why did you shoot HD if you needed 2K?
It seems to me the logical way to do this would be to scale the 2K to HD, edit in HD, export as HD, let some professional house upscale it with software designed to take HD to 2K. My guess is that there is a lot of that going on.