GWAS Retrieve Target Sample from a whole set of samples and PRS in PRSice tool

Question

[landscape95]

Hi everyone, I am trying to calculate the PRS for the Target Samples in GWAS, I only have the bed/bim/fam file Plink format, after I calculate the SNP effect, now I don't know who to extract the Target from a bunch of samples in the whole data for PRSice tool. Does anyone know how to deal with this situation since as I know, there is no way to recreate a bed file with a selected target samples from fam file. Your help is really appreciated!