mysql - SQL order by convert -

i have problem ordering query converting longtext (b.meta_value) datetime. getting error 1064. format in database mm/dd/yyyy , i tried order by, keep getting error 1064. problem?:

convert(convert(b.meta_value,char(30)),datetime, 101) convert(datetime, convert(b.meta_value,varchar(30)), 101) convert(datetime, str_to_date(b.meta_value, '%m/%d/%y'), 101) 

here query:

select  d.name name, b.post_id post_id, b.meta_value meta_value  wp_posts  inner join wp_postmeta b  on a.id=b.post_id  inner join wp_term_relationships c  on c.object_id=b.post_id  inner join wp_terms d  on c.term_taxonomy_id=d.term_id  meta_key in('px_event_from_date')    , a.post_type='events'    , a.post_status!='trash'    , d.term_id = 104    , str_to_date(b.meta_value, '%m/%d/%y') <= curdate()  order convert(datetime, str_to_date(b.meta_value, '%m/%d/%y')) desc  limit 0,1 

you should set meta_key filter in join meta_key = 'my_date' (because don't know meta key trying catch):

select  d.name name, b.post_id post_id, b.meta_value meta_value  wp_posts  inner join (   select       post_id,      meta_value   wp_postmeta    meta_key = 'my_date' ) b  on a.id=b.post_id    ,  str_to_date(b.meta_value, '%m/%d/%y') <= curdate()  inner join wp_term_relationships c  on c.object_id=b.post_id  inner join wp_terms d  on c.term_taxonomy_id=d.term_id  meta_key in('px_event_from_date')    , a.post_type='events'    , a.post_status!='trash'    , d.term_id = 104  order str_to_date(b.meta_value, '%m/%d/%y') desc  limit 0,1