It would help you to find out from SRR file description what exactly is present in the repository, as that will make it easier to understand. Beyond that, looking through file headers should also give an answer as paired-end reads will have the same headers. "Left" reads will likely have either :1 or /1 in their headers, while "right" reads will have either :2 or /2. Simply typing head file (where file should be replaced by an actual name) might give you enough information to match the reads.