https://{Your_Domain_URL}/services/data/v56.0/limits/recordCount can be used to find the number of records in each Salesforce Object using REST API.
Workbench:
Postman Client:
How to find number of records in each Salesforce Object using REST API?
https://{Your_Domain_URL}/services/data/v56.0/limits/recordCount can be used to find the number of records in each Salesforce Object using REST API.
Workbench:
Postman Client: