I suppose we could have a war of semantics about whether there’s a difference there, but I think we agree on the general principle–see a lawyer, you don’t have much time. 
I’ve seen both cases of companies firing or wanting to fire “the 6 people who’ve been in the job the least time” and of companies wanting to fire “the 6 people who’ve been in the job the longest.” The first ones were thinking “we’ll have to pay less for firing them, as the payout is based on time worked” the second ones “those are the ones who are more likely to be on the high end of their salary range, so we save more on payroll by firing them.”
If you do not know how to find an employment attorney, your state bar association probably has a referral service. Google “[state] bar association referral” and you should find something. If not, PM me your state and I’ll give it a whirl.