Sent LTC with no fee, now gone?

As topic says.

i created a litecoin wallet in 2014 with an old litecoin qt.

a few days ago i sended them to my coinbase account without any fee( didnt know that i should set it my self).
it showed up directly in my coinbase as pending, after 2 days it disappeared from transactions in Coinbase and i cannot track the transaction either, but i see my sent transaction in my wallet.

is it gonna show up later in my wallet or do i have to do anything?

or now when i have the litecoin qt wallet, is it safe to install litecoin core wallet on same computer and take the wallet.dat file into that wallet, because in my litecoin qt wallet i have no abandon button.

or should i install it into a new computer and import the wallet.dat?

right click the transaction and click cancel / abandon transaction …as long as it has not confirmed yet…
it wont confirm without that fee for a very very very long time

make sure there is only one copy of the wallet.dat file in the Appdata folder…your backup (renamed wallet.dat)