I have read the docs from twitter-ads-api metrics-and-segmentation. It seems no metric related with ads spend like the spend column on the dashboard from ads_manager.

Can someone help?

Thanks

Unfortunately, the naming between the Ads Manager UI and the Ads API is not consistent. The documentation for the BILLING metric group describes billed_engagements and billed_charge_local_micro. I would recommend consulting this documentation and reviewing other threads on this forum for information on mapping the UI names to the Ads API names.