To use this in GNS3, you would need to convert it to a format QEMU understands (very difficult and unstable). Therefore, the better path is to download an from Cisco’s virtual lab offerings.
Cisco protects its IOS images under copyright law. You cannot legally download a 2960 IOS from a public torrent or file-sharing site without owning a corresponding hardware device and a valid service contract. GNS3 does not provide any proprietary images—you must supply your own. cisco 2960 switch ios download for gns3
Legal downloads require a Cisco account and a paid subscription. How to upload the Cisco Switch 2960x image into GNS3 To use this in GNS3, you would need