You may want to explore the descriptions, and use the comparison tool, at iPad - Apple .
It looks like most of the models weigh about a pound, except for the iPad mini (two-thirds of a pound) and the 12.9" iPad Pro (one and a half pounds). Most now have USB-C (the Pros also have Thunderbolt). Storage options are 64 GB or 256 GB on all of the models except the Pros, where you can get up to 2 TB. The Pros use Face ID; the others, Touch ID.
The iPad Air and iPad Pro have much more RAM than the others. These three models support Stage Manager . The regular iPads and iPad Minis don't.
I don't know what your budget and needs are, but personally, I'd be reluctant to buy
- the last-generation (9th-generation) iPad, which is dated compared to the others
- the 12.9" iPad Pro, as nice as it is, because of its significantly higher weight
- any iPad with only 64 GB of storage – I have more than that on my iPhone
Rough comparison guide (based on Apple site and MacTracker)
iPad Pro – 11.9" (4th generation) and 12.9" (6th generation)
M2 processor. 128 GB to 2 TB of storage. 8 GB of RAM – or 16 GB on models with 1 TB or 2 TB of storage.
Liquid Retina display with P3 wide color. Fully laminated with anti-reflective coating.
12.9" model has mini-LED backlit display for playing HDR video content, but weighs 1.5 pounds.
USB-C port has support for USB4 and Thunderbolt.
Two rear cameras, instead of just one.
From $799 / $999 USD (11.9" model) or $1099 / $1299 USD (12.9" model).
iPad Air (5th generation) – 10.9"
M1 processor. 8 GB of RAM.
Liquid Retina display with P3 wide color. Fully laminated with anti-reflective coating.
From $599 / $749 USD.
iPad – 10th generation (10.9")
A14 Bionic processor. 4 GB of RAM (source: MacTracker).
Liquid Retina display with sRGB color (not P3 wide color).
From $449 / $599 USD.
iPad – 9th generation (10.2")
A13 Bionic processor. 3 GB of RAM (source: MacTracker).
Retina display with sRGB color (not P3 wide color).
No USB-C port – instead, there is a Lightning port (a legacy port now being phased out).
Wi-Fi 5 (older version). No 5G – just LTE (data only) on cellular models.
Wide camera has only 8 MP. Cannot take 4K video (all the others can).
From $329 / $459 USD.
iPad mini – 6th generation (8.3")
A15 Bionic processor. 64 GB or 256 GB of storage. 4 GB of RAM (source: MacTracker).
Liquid Retina display with P3 wide color. Fully laminated with anti-reflective coating.
From $499 / $649 USD.