Converting between units for thermal conductivities (BTUs involved)

[mclame22]

The thermal conductivity of wood is 1 BTU per hour, per square foot, for a temperature gradient of 1 F° per inch. Convert this to units of W/mK, knowing
1 F° = 5/9 C°
1 inch = 0.0254 m
1 foot = 0.3048 m
1 lb = 0.453593 kg
1 kcal = 4184 JI know there are conversions between BTU and joules/calories, but he says looking this up will cost us half of the question. So far all I've concluded (I think) is that the unit we need to convert is
BTU·inch / hr·ft²·F°

But I'm not sure how to get rid of the BTU without knowing a conversion factor... If I can get rid of the BTU I'm sure I'll be able to figure the rest out. Is there a way to do it without knowing anything else, maybe by using the definition of a BTU?
I'm also confused about the difference between a degree Fahrenheit (°F) and a Fahrenheit degree (F°).

 

[omoplata]

I agree that you can use the definition of BTU to find how many joules a BTU is. But are you allowed to use it?

About Fahrenheit, I THINK both are the same.