"长大到能穿着" 可以表达为 "grow old enough to wear" ，不过更自然常用的表达可能是 “grow up to the point of being able to wear” 或者更简洁的 “be old enough to wear” 。例如：
You'll be old enough to wear that formal dress when you're a bit taller.（等你再长高一点，就够年龄穿那件正式礼服了。）
I hope I'm old enough to wear high heels soon.（我希望我很快就能长大到可以穿高跟鞋了 。）