I try to import contribution. Procedure - Contribution - import contribution - import the .csv list
Error "is not a valid option for field campaign_id"
Where do I find the campaign_id?
If you contributions belong to a campaign, you can find out the id by visiting the campaign dashboard (/civicrm/campaign?reset=1) and hover over the edit link on the right side. You will see a link like the one below - the last number is your campaign ID.
However, if your contributions do not belong to campaigns, I guess you would probably not have to set them when importing?