This is not a currently supported feature of ECR so you would need to perform the following steps to migrate from one account to another:

• aws ecr get-login-password --region <region> | docker login --username AWS --password-stdin <aws_account_id>.dkr.ecr.<region>.amazonaws.com - Run this for the source account
• docker pull $SOURCE_IMAGE:$VERSION - Pull the latest tag down to your local
• docker tag $SOURCE_IMAGE:$VERSION $TARGET_IMAGE:$VERSION - Tag a new image based on the original source image
• aws ecr get-login-password --region <region> | docker login --username AWS --password-stdin <aws_account_id>.dkr.ecr.<region>.amazonaws.com - Run this for the target account
• docker push $TARGET_IMAGE:$VERSION - Push the docker image upto the target ECR account.

If you want to move all repositry from particularly region to another account (Destination account) then use below script.

• It will list all repo from Account A
• Pull an image from an account A one by one
• Create Repo in Account B
• Tag image
• push image to account B

#!/bin/bash
TARGET_ACCOUNT_REGION="us-west-2"
DESTINATION_ACCOUNT_REGION="us-west-2"
DESTINATION_ACCOUNT_BASE_PATH="123456.dkr.ecr.$DESTINATION_ACCOUNT_REGION.amazonaws.com/"


REPO_LIST=($(aws ecr describe-repositories --query 'repositories[].repositoryUri' --output text --region $TARGET_ACCOUNT_REGION))
REPO_NAME=($(aws ecr describe-repositories --query 'repositories[].repositoryName' --output text --region $TARGET_ACCOUNT_REGION))


for repo_url in ${!REPO_LIST[@]}; do
        echo "star pulling image ${REPO_LIST[$repo_url]} from Target account"
        docker pull ${REPO_LIST[$repo_url]}


        # Create repo in destination account, remove this line if already created
        aws ecr create-repository --repository-name ${REPO_NAME[$repo_url]}
        docker tag   ${REPO_LIST[$repo_url]} $DESTINATION_ACCOUNT_BASE_PATH/${REPO_NAME[$repo_url]} 
        docker push $DESTINATION_ACCOUNT_BASE_PATH/${REPO_NAME[$repo_url]} 
done

Make sure you already obtain login token for both account or add these command in the script.

        aws ecr get-login-password --region $TARGET_ACCOUNT_REGION | docker login --username AWS --password-stdin ${REPO_LIST[$repo_url]}
        # destination account login, make sure profile set for accoutn destination
        aws ecr get-login-password --region $DESTINATION_ACCOUNT_REGION --profile destination_account | docker login --username AWS --password-stdin ${REPO_LIST[$repo_url]}

aws-cli-cheatsheet

Or you can use one of them

• AWS cross-region replication
• Cross account replication

Amazon ECR uses registry settings to configure features at the registry level. The private registry settings are configured separately for each Region. Currently, the only registry setting is the replication setting, which is used to configure cross-Region and cross-account replication of the images in your repositories

cross Region/account Replication feature in AWS

AWS has launched CRR (Cross Region Replication) and CAR (cross account replication)Click here for more info