Good morning, dawnshell1313!
Your current plan is $140 + tax. The T-Mobile One plan would be $160 for all four lines if you have autopay set up. If you don't have autopay set up it would be $180 for all four lines. In the end, the cost may be about the same depending on how much you pay in taxes/government fees on your current plan as switching to T-Mobile One would include those fees in the price.
You'll lose your Data Stash by switching to this plan but you won't need it since you'll have unlimited data. Also, the T-Mobile One plan is not eligible for monthly discounts via your employer/government.
Please let me know if you have any other questions that I can answer for you.