My bag was stolen with my 3 Pakistani passports having US, UK & Canada visas. Can anyone guide me how to get the visas back, on my new passports?
This answer assumes you are not in any of the three countries mentioned.
US: To replace a visa from outside the USA, you must apply in person at a U.S. Embassy or Consulate abroad. When applying for the replacement of a visa, you will need to provide a written account documenting the loss of your passport and visa. Include a copy of the police report. https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/lost-stolen-visas.html
UK: You need to apply for a replacement using transfer of conditions. A police report or other evidence that satisfactorily establishes that the passport is no longer in your possession is required. https://www.gov.uk/transfer-visa
Canada: it looks as if you can’t replace a lost or stolen visa from outside Canada. You will need to apply for a new visa. http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=044&top=12