What is the best way to obtain contact information and dates of jobs that I worked for the last 7 years, free?

I am applying for a job, and the application requires that I list all the jobs that I worked, along with the contact information and dates that I worked. How can I get this information free of charge?What is the best way to obtain contact information and dates of jobs that I worked for the last 7 years, free?Check your W2's from previous filing years