Hi Jesca,
Thank you for reaching out to us. I see that you have two concerns. You can find my response to them below.
1. Do I still need a Link ID to track app conversion?
You'll need a Link ID if you're using
Mobile App Conversions and Remarketing API. For conversions under Google Ads/AdWords API, you won't need a Link ID.
2. How can we know the external customer ID associated with our Google Ads manager account?
You can find your customer ID for your manager account by logging into the Google Ads UI, and then clicking the "?" button in the upper right hand corner. The drop down that comes from that should list your Manager Account ID number.
Let me know if you have further questions.
Thank you,
Bryan, Google Ads API Team

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