Say 'three ears', running the words together. There is a /j/ sound in the glide from the vowel of 'three' to the diphthong of 'ears' In normal conversation, there is very little difference between the sound of 'three ears' and that of 'three years'. Try to hold the position of your tongue as you move from 'three' to ears' - that is the position for /j/. Try to produce just that sound.
Say 'long ears'; now try to insert the /j/ when you say 'long years'.
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