how can i search in p-blast against UNIPROT(not only swissprot)

I don't know of any online tool enabling a search against TrEMBL. You probably will have to set up your own local BLAST environment, roughly following these steps:

1. download blast+ - but there might be an easier way to install the software, depending on your operating system (e.g. on Ubuntu you can just sudo apt install ncbi-blast+)
2. download target databases
3. build local database

I hope this helps.