so i basically just had a mini heart attack because i realized i have no idea how my new camera works and i leave for my big trip to the grand canyon and yellowstone in literally eleven days. i bought this used sony a6400 because everyone says they are the best but it only came with this tiny flat lens that barely zooms at all. i tried to take a picture of a squirrel in my backyard today and it looked like a tiny gray dot so there is no way i am gonna get good shots of elk or whatever else is out there. i am a complete beginner like i didnt even know the lenses come off until yesterday so please talk to me like i am five years old lol. i have been looking online for a zoom lens but everything is so expensive like why are they $1,500?? i only have about $350 or maybe $400 if i skip a few meals on the trip to spend on this and i really need something that can see far away. i keep seeing stuff about 70-300 or 55-210 and i dont know what the numbers mean or if they even fit my camera. my main goals are:

• taking pictures of wildlife from far away
• not spending more than $450 max
• something that isnt too heavy to carry on a hike

someone mentioned something about "crop sensors" vs "full frame" and my brain just melted. i just want one lens that i can put on and leave there that lets me zoom in really close to animals and mountains without it being all blurry and dark. is there a specific brand like tamron or sigma that is cheaper but still good? or do i have to stay with sony? i am so stressed because i dont want to get there and realize i cant take any good photos after spending all this money on the actual camera body. what is the absolute best budget zoom lens i can get for a sony that wont make me go broke? i really hope i didnt make a mistake buying this thing...