PRISM output file is a compressed tar zip file.

Open a Unix/Linux shell. Type the command:

tar -xzvPf outputFile

You will get a bunch of files. 

File ending with ".ampl.out" has amplicons' primer name, sequence and conservation score.
File ending with ".ampl.fasta" has amplicons' sequence in fasta format.
File ending with ".pri" has all valid primer candidates.
File ending with ".pri.fasta" has all valid primer candidates in fasta
format.
File ending with ".pri.de" has all valid and invalid primers with
degenerate bases.
File ending with ".pri.invalid" has all invalid primers with reasons.
File ending with ".pri.iupac.conserv" has all valid and invalid
primers with conservation score. 
File ending with ".major" has the major consensus sequence of all genomes. 
