Field ID (@fieldID) is varchar with values 61, 9 which you are using in IN, which will not work
SELECT c.ColumnName,q.QuestionTypeID FROM tblColumns c
INNER JOIN tblQuestions q ON (c.QuestionnaireID=q.QuestionnaireID AND c.QuestionID=q.QuestionID)
WHERE c.QuestionnaireID=284 AND c.QuestionID IN (@fieldID)
One option is to declare 2 variables and use them:
DECLARE @fieldID1 INT = 61
DECLARE @fieldID2 INT = 9
SELECT c.ColumnName,q.QuestionTypeID FROM tblColumns c
INNER JOIN tblQuestions q ON (c.QuestionnaireID=q.QuestionnaireID AND c.QuestionID=q.QuestionID)
WHERE c.QuestionnaireID=284 AND c.QuestionID IN (@fieldID1, @fieldID2)
Other option is to use a split function and convert the array into temp table and use the same.