For our American friends, the EOS3000n was apparently sold as the 'Rebel XS N', while it was sold as the EOS66 in Asia.
The Canon EOS1000F (I'm not familiar with the F n?) was sold in the Us as the 'Rebel S'.
I can't comment on the EOS 3000n as I've never used one. I have a Canon EOS1000F here, which in fact is the very first EOS camera I ever handled when I was...IDK, probably 9 or so? Like many of the entry-level EOS cameras, it's a functional machine that yields perfectly fine results. There are two issues with it; one is a minor nuisance, the other is more problematic. The nuisance is that it's a noisy camera. It used the same kind of noisy motors for film transport that e.g. the Canon T90 and the very first EOS1 (not -N) used. Compared to your EOS 300v, the 1000F will feel and sound clunky.
The more severe problem is one that affects many of the older EOS bodies: the sticky shutter syndrome. This is apparently glue or dissolved material from the mirror damping foam that leaks unto the shutter blades and sticks them together. This can often be carefully cleaned off with a q-tip and ethanol or isopropyl alcohol, but the problem can return (as the goo keeps on oozing). It's usually apparent initially as distinct shutter capping at higher speeds (1/1000 is typically affected), leaving part of the frame blank/unexposed. It then gets progressively worse. The issue is easily diagnosed as the patch of shiny, black, tar-like substance on the shutter is very apparent on the shutter with the camera back opened.
A camera that's (still) unaffected by this issue is functionally comparable to the EOS300v you already have. In fact, they filled more or less the same spot in the product line-up, just in different eras. The 1000F was the entry-level EOS sold at around 1989-1990 aimed at amateur photographers. The EOS300v was the same, just a decade later.
The build quality of the EOS1000F is IMO more solid than the EOS300v's, but it's questionable that this makes a whole lot of difference in daily use. The EOS300v is a little more compact and I assume it's also lighter in weight.
inside the view finder is possible to have numbers that show exposure ?
On the 1000F, yes. It shows shutter speed and aperture IIRC, there's an AF confirmation (green 'dot') and an indication for over/underexposure when using e.g. manual exposure mode.
AFAIK the metering patterns are the same on the 1000F and the 300v. It's possible that the 300v's evaluative metering mode (the one used by default on 'green' mode) is better trained at diverse lighting conditions than the much older system on the 1000F.
If you want a modestly priced upgrade from your 300v, consider an EOS30v or an EOS50e.