Hola
Welcome to the forum.
It really depends on what your plan is
Such as if you intend to continue traveling afterwards, what time of year you plan to walk, how many km you think you will walk daily.
If your plan is to walk during spring, summer, autumn you may not need sleeping bag, warm cloths, thermos and such.
This will reduce your pack items and thereby your backpack.
As stated above, the distance can be done in 5-7 days and if you only have to carry gear for that distance, you can easily do the walk with a very small backpack.
Remember that you will be walking through rural areas with plenty of food, water and shops that sells everything you may need.
You could even go real easy with only the cloths you are wearing, a poncho, some personal items and that's it.
All depends on your wish for your camino experience.
Buen Camino
Letinggo