plentiful / plenty of / plenty

  1. In those days jobs were plentiful.
    1a. In those days jobs were abundant.
  2. In those days plenty of jobs were there.
    2a. In those days abundant jobs were there.
  3. There is plenty of milk in the fridge.
    3a. There is a lot of milk in the fridge.
  4. We have plenty of work to be done.
    4a. We have plenty work to be done.
    Please correct them all.
    Thanks.
  1. In those days there were plenty of jobs.
    In those days there was an abundance of jobs.

3 and 3a do not mean the same.

4a is incorrect.

Beeesneees,
Could you please explain the meanings of #3 and #3a and show how they are differing in the meanings?
Thanks.

Beeesneees,

  1. In those days plenty of jobs were there.
  2. In those days there were plenty of jobs.
    You have branded #1 is wrong.
  3. In those days jobs were there.
  4. In those days there were jobs.
    Is #3 wrong while #4 is correct?
    Please explain the grammar points involved here to understand better.
    Thanks.

plenty of - enough for the required purpose
a lot of - a large amount

The standard word order is
‘There were plenty of jobs.’

‘In those days there were jobs there’
is actually more fluent than
‘In those days jobs were there.’