For not having any experience this is a lot like a non-runner asking how to run a marathon. You should probably start smaller with a couch-to-5k approach and work your way up to it. Going too hard too fast is an easy way to have a terrible experience. I've watched far too many people abandon the hobby because their first attempt was too ambitious and they got in over their heads.
If you're really starting from zero my recommendation would be to get yourself a decent pair of trail shoes and a small day pack. Find some short local day hikes and hit the trail for a couple of hours on the weekends. Mix in a little car camping and see how it goes. If you have friends who have gear, start by borrowing what you can and if the camping/hiking bug bites you slowly start building out your own set of gear. If you don't have friends that backpack find some and go on an overnight trip away from the cars. Ask them about the gear they brought and why. They'll have lots of opinions.
After you get a bit more comfortable with the basic stuff and have a better sense for what you need then start planning a longer trip like this.
I guess at that point you just need to start doing it. I have a lot of outdoorsy types in my family and we've been doing long, multi-day backpacking trips most summers since 1998. On my first trip I bought a cheap sleeping bag, pad, and backpack and relied on the more experienced people in the group for everything else. The shoes I wore were terrible and by the time we got back to the car on the end of the 4th day I could barely walk my feet were so blistered. For the next summer I saved up and bought a really nice pair of boots which I still have. They're the most expensive footwear I've purchased in my life and worth every penny.
I can't recommend enough finding a group of experienced people to start with. You'll make plenty of mistakes and they'll help keep it from turning into a catastrophe. You'll pick up a lot from them while also figuring out what does/doesn't work for you. Probably five years after starting backpacking with my family I was the 'experienced one' leading a group of friends on a hike through the Smokey Mountains on the Appalachian Trail.
Start rock climbing, take an intro to mountaineering course with a guiding service (lots of them in WA, OR, CA), or find someone to introduce you to it.
When we do an Intro to Backpacking weekend as part of our Spring hiking program, we tend to go in a relatively short distance to a lake/pond or something along those lines. And then will do one or two day hikes from there. This gives plenty of time to experiment with gear, setting up/breaking down camp, and so forth without the time pressure of having to get to some destination. (But you still get a sense of pack weight and so forth.)
If you're really starting from zero my recommendation would be to get yourself a decent pair of trail shoes and a small day pack. Find some short local day hikes and hit the trail for a couple of hours on the weekends. Mix in a little car camping and see how it goes. If you have friends who have gear, start by borrowing what you can and if the camping/hiking bug bites you slowly start building out your own set of gear. If you don't have friends that backpack find some and go on an overnight trip away from the cars. Ask them about the gear they brought and why. They'll have lots of opinions.
After you get a bit more comfortable with the basic stuff and have a better sense for what you need then start planning a longer trip like this.