How to create a physical/paper backup for bitcoin-core wallet?
if I generated 100 addresses and transferred some BTC to all of them, I need to backup all the 100 addresses.

Bitcoin core is an HD wallet. So you should only need to backup the extended master private key shown at the top of dumpwallet.

# Wallet dump created by Bitcoin v0.21.0
# * Created on 2021-05-05T17:57:09Z
# * Best block at time of backup was 627544 (000000000000000000045a465b959072a715f47047141108ef14db64e2ee9049),
#   mined on 2020-04-25T08:34:02Z

# extended private masterkey:
xprv1x23XxXX456X7XXXXxxXx8Xxx9XxXxXxX01234X5xxX6XxX7xXxxXXXXxXxxXxx8X9Xx0XX1XxxX2XXx3x45xx6xxxXXXxxxxX7XXXxx8XX  


etc
Obviously you should practice recovery from this , and check the recovered balance, on a different computer, before relying on it. At least check that the generated subsidiary keys/addresses are the same.
It may be easier to recreate the wallet from an extended master private key (xprv) by using wallet software like Electrum, which has some support for this. Bitcoin core expects you to backup the wallet.data file rather than write down a number on paper.

Related

How to restore Bitcoin Core HD wallet private keys by master key?
How do I retrieve my backed up wallet to Bitcoin Core?