I have set up my service account and I can run queries on bigQuery using client.query().

I could just write all my scheduled queries into this new client.query() format but I already have many scheduled queries so I was wondering if there is a way I can get/list the scheduled queries and then use that information to run those queries from a script.

Yes, you can use the APIs. When you don't know which one to use, I have a tip. Use the command proposed by @Yev

bq ls --transfer_config --transfer_location=US --format=prettyjson

But log the API calls. for that use the --apilog <logfile name> parameter like that

bq --apilog ./log ls --transfer_config --transfer_location=US --format=prettyjson

And, magically, you can find the API called by the command: https://bigquerydatatransfer.googleapis.com/v1/projects/<PROJECT-ID>/locations/US/transferConfigs?alt=json

Then, a simple google search leads you to the correct documentation

In python, add that dependencies in your requirements.txt: google-cloud-bigquery-datatransfer and use that code

from google.cloud import bigquery_datatransferclient = bigquery_datatransfer.DataTransferServiceClient()
parent = client.common_project_path("<PROJECT-ID>")
resp = client.list_transfer_configs(parent=parent)
print(resp)