Adding item to target list from source list using CSOM

Try below code. which will copy all the field values from source to destination.

srcContext = new ClientContext(mpObject.SourceSiteCollection.SiteURL);
                targetContext = new ClientContext(mpObject.TargetSiteCollection.SiteURL);

            List<Field> srcFieldCollections = new List<Field>();
            List srcList = srcContext.Web.Lists.GetByTitle(listName);
            srcContext.Load(srcList);
            srcContext.ExecuteQuery();

            CamlQuery camlQuery = new CamlQuery();
            camlQuery.ViewXml = "<View/>";

            ListItemCollection srcListItemCollection = srcList.GetItems(camlQuery);
            srcContext.Load(srcListItemCollection);
            srcContext.ExecuteQuery();
            ListItemCreationInformation targetItemCreationInfo = new ListItemCreationInformation();
            ListItem targetListItem = targetList.AddItem(targetItemCreationInfo);

            foreach (ListItem sourceItem in srcListItemCollection)
            {
              foreach (Field field in sourceItem.Fields)
              {
                targetListItem[field.InternalName] = sourceItem[field.InternalName] ;
              }
              targetListItem["Title"] = sourceItem["Title"] ;
            }
            targetListItem.Update();
            targetContext.ExecuteQuery();