How would I find an electronic copy of a W2 from a previous employer?

TurboTax does not have a copy of your W-2—the Wage & Tax Statement—issued to you by your employer.  You should always save those documents for your own records. You could ask the employer(s) for copies or you can get a copy from Social Security (for a fee).

https://faq.ssa.gov/link/portal/34011/34019/Article/3836/How-can-I-get-a-copy-of-my-wage-and-tax-statements-Form

You can also get a free Wage and Income transcript here:
<a rel="nofollow" target="_blank" href="https://www.irs.gov/individuals/get-transcript">https://www.irs.gov/individuals/get-transcript</a>