ABIs of verified smart contracts can be downloaded from block explorers like Etherscan. For your Uniswap V2 router, you can find it by searching for the contract address here (scroll down to Contract ABI section).

The ABI you need is typically a JSON file that you can import into your dApp.

You can also often find ABIs in the official GitHub repositories of the protocol’s smart contracts. In the future, it’s usually more effective to join a project’s Discord or seek support from the community rather than posting on StackOverflow.