What kind of scar removal cream can I use on long scar?

Improve not remove. There is no scar cream that will remove a scar. The proper cream depends on the condition of the scar. Most consist of silicone geeks mixed with some sunblock. Others contain vitamin e, antioxidants, onion extract (me derma), steroids, bleaching agents, moisturizers, etc. The effectiveness of these other agents is debated and their benefits may depend on the individual characteristics of the scar.
No such cream. There are no "scar removal creams" since a scar is permanent. One can massage scars with various creams that would eventually allow for reducing pinkness. If the scar is brown or hyperpigmented, one can lighten or bleach the scar with certain bleaching creams. Massaging with most good moisturizing creams can benefit most early scars.
Scar cream. No cream or gel can completely "erase" a scar, but there are many that can significantly help to fade and soften scars. Looks for products with silicone or dimethicone as the active ingredient, as these ingredients have been clinically shown to improve scars.
Options. The simplest option may be a steroid tape. Otherwise, scarguard is beneficial as well.