Clone Factory in Upgradeable smart contract(UUPS proxy) - ethereum

Question

When we use the Create clone factory approach the initialize function takes in the address of the deployed address(_recardAddress) whom we want to clone. In the case of upgradeable contract we get two contracts that is the "Proxy" and "implementation". So whoes address do we have to pass in to the initialize function and why?
I tried passing in the implementation contract address and it works but dont know the reason!
# THIS IS THE FACTORY CONTRACT WHICH MAKES THE CLONES
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;
import "./BlockCard.sol";
import "./CloneFactory.sol";
import "#openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "#openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
import "#openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
contract BlockCardFactory is Initializable,CloneFactory,OwnableUpgradeable,UUPSUpgradeable{
address public BlockCardAddress;
address[] public clonedcontracts;
event BlockCardCreated(address newBlockCard);
//initialising
function initialize( address _recardAddress) initializer public{
BlockCardAddress=_recardAddress;
__Ownable_init();
}
//creating clone
function createBlockCard() public {
address clone=createClone(BlockCardAddress);
BlockCard(clone).initialize();
clonedcontracts.push(clone);
emit BlockCardCreated(clone);
}
//adding into the array
function getAddress(uint i) view external returns(address){
return clonedcontracts[i];
}
//interaction with cloned addresses
function interwithClone(address arr)public view returns(string memory){
BlockCard cloned=BlockCard(arr);
return cloned.getname();
}
//UUPS
function _authorizeUpgrade(address newImplementation)internal override onlyOwner{}
}
#THIS IS THE CONTRACT WHICH NEED TO BE REPLICATED
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;
import "#openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "#openzeppelin/contracts-upgradeable/proxy/utils/UUPSUpgradeable.sol";
import "#openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
contract BlockCard is Initializable,UUPSUpgradeable,OwnableUpgradeable {
struct Person{
string name;
string gender;
uint age;
string bloodgroup;
string DOB;
}
Person person;
function initialize() initializer public{
__Ownable_init();
}
function getname() public view returns(string memory){
return person.name;
}
function setName(string calldata _name) public {
person.name=_name;
}
function setGender(string calldata _gender) public {
person.gender=_gender;
}
function setAge(uint _age) public {
person.age=_age;
}
function setBloodgroup(string calldata _bloodgroup) public {
person.bloodgroup=_bloodgroup;
}
function setDOB(string calldata _DOB) public{
person.DOB=_DOB;
}
//UUPS
function _authorizeUpgrade(address newImplementation)internal override onlyOwner{}
}