Contact the former employer. They are obligated by law to supply that
information to you. Use the following link https://www.irs.gov/uac/irs-can-help-if-w2s-are-missing
in order to contact the IRS if the former employer is reluctant to
help you. The IRS will attempt to match your
income to the information it has received from the former employer(s). If you
file without the actual W-2, then you're running the risk of getting an IRS notice
that says your income doesn't match their records.
The employer is
required to make every effort to get you your copy of the W-2.
If all attempts prove to be fruitless, you'll file a Form 4852 Substitute for Form W-2.