I finally got Tmobile home internet yesterday, but the laptop that my wife uses does not see the internal router.  I think if I connected to an external router I could get it working again.  This begs the question, shouldn't I go ahead and get a mesh system to broadcast wifi across my house and potentially to my detached garage better?  What mesh systems do you generally recommend?  I'd optimally prefer something I could pick up today locally at Walmart, Sams, or Best Buy.  But if ordering from Amazon or where ever is my best bet then we can go that way.  

Thanks in advance.

I've been a huge fan of the orbi ones. Also make sure the WiFi driver is up to date on your wife's laptop.

Define detached garage.  A few feet from the house or the other side of 10 acres?

Not high priority.  If I can't get good wifi signal there is is not a problem at all.  

However, a steel sided pole barn with 3 garage doors facing the house.  About 80 feet from the side of the house.

If you place your current wifi router in the closest location to the barn so you get signal? If not you probably won't still with mesh and you might want to go wifi extender which is better for pushing wifi far away but does not have the seamlessness of mesh.

Okay, forget about the barn.

Is the Orbi the best thing to get?

Then yes. If you have a 2 story home top floor facing the barn is probably the best bet on the mesh and you might just barely make the jump to a well placed satellite orbi

The Costco 3 pack has been good to me.

Forget the consumer crap.

Buy a Unifi Dream Machine:

https://store.ui.com/collections/unifi-network-routing-switching/products/unifi-dream-machine

Add mesh points IF you need them.

i just installed a eero pro 5 mesh unit in my house. i picked it up at best buy for 499. it works great and super easy to set up.