Hi,
The [https://www.amazon.com/GinTai-Charging-Replacement-ChromeBook-C740-C3P1/dp/B01M8QBM38|DC In jack] (supplier example only) is hard mounted onto the motherboard. There are other suppliers online that may suit you better. Just search for ''Acer Chromebook C740 DC-In jack'' to get results.
Here’s the ifixit [guide|89205] guide.
This shows how to remove the motherboard from the laptop so that the DC-In jack can be unsoldered and a new one soldered in its place.
If doing this yourself seems too daunting, contact a reputable, professional laptop repair service and ask for a quote.