Where to find API name for standard field of standard object in Salesforce?

Hi,

There are a couple of ways:
1-In Salesforce, go to set up> Object Manager> Find the object and click on Fields & Relationships. You'll see the API names as well as whether the field is custom or standard
2-Go to https://developer.salesforce.com/docs/atlas.en-us.sfFieldRef.meta/sfFieldRef/salesforce_field_reference.htm and search for an object (ie Account). You'll have a list of all the standard fields and their API names
3-Use the API to extract objects and their fields. You can use the data laoder for this, or workbench, dataloader.io, there are plenty