Clicking the 'More' button on the WolframAlpha[] output, then obtain the Number data (see GIF below). The call we get is
WolframAlpha["integers | perfect square and having 9 digits",
{{"Result", 1}, "NumberData"}, PodStates -> {"Result__More"}]
{100000000, 100020001, 100040004, 100060009, 100080016, 100100025, 100120036,
100140049, 100160064, 100180081, 100200100, 100220121, 100240144, 100260169,
100280196, 100300225, 100320256, 100340289, 100360324, 100380361}
We can simulate multiple button clicks. Here's two:
Length @ WolframAlpha["integers | perfect square and having 9 digits",
{{"Result", 1}, "NumberData"}, PodStates -> {"Result__More", "Result__More"}]
20
Unfortunately there's either a timeout or a memory limit was hit and we can only get up to 9 button clicks:
Length@WolframAlpha["integers | perfect square and having 9 digits",
{{"Result", 1}, "NumberData"}, PodStates -> ConstantArray["Result__More", 9]]
5120
WolframAlpha["integers | perfect square and having 9 digits",
{{"Result", 1}, "NumberData"}, PodStates -> ConstantArray["Result__More", 10]]
Missing["NotAvailable"]

and having 9 digitswithand greater than 100160064will return the next 10. Repeat as needed. Or perhaps the paid subscription to WolframAlpha will return more data. I've never seen a sufficiently detailed description of the features to coax me into paying for that. $\endgroup$